Question: Simplify the following expression: $k = \dfrac{a}{2} - \dfrac{5a}{8}$
In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $2$ and $8$ $\lcm(2, 8) = 8$ $ k = \dfrac{4}{4} \cdot \dfrac{a}{2} - \dfrac{1}{1} \cdot \dfrac{5a}{8} $ $k = \dfrac{4a}{8} - \dfrac{5a}{8}$ $k = \dfrac{4a -5a}{8}$ $k = \dfrac{-a}{8}$